This is the first Compression/Sustainer pedal released from Boss. It builds on the lagacy
of the Roland AS-1. Like all compression pedals it reduces the output of sounds over a set
threshold relative to the strength of the input signal, making levels consistent and improving
sustain. In the CS-1 this is done by means of photocouplers. The later CS-2 and CS-3 used VCA's
(Voltage Controlled Amplifier) to create the same effect. The sound of the CS-1 is thus very
different from its successors.